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Letter 27037
Coating for aluminum heat sink
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I have an aluminum heat sink used in a cleanroom environment and
therefore the surface needs to sealed to prevent oxidiation and
contamination to sensitive materials. Will a chromate coating have
sufficient thermal conductivity to ensure good heat transfer? And is
chromate a sacrificial coating or will it resisit oxidation even if
scratched? If the answer to these questions is 'no' than what would
be the best coating to use?
Jim Sbrogna
Semiconductor Equipment Engineer - Natick , Massachusetts
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Ideally, heat sinks should be anodized. Chromate coatings will not
cause thermal conductivity problems, but they are electrically
conductive, which could be a problem. Chromate is not a sacrificial
coating but it is "self healing" so it is helpful even in an
environment where scratching is possible.
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Ted Mooney, P.E.
finishing.com
Brick, New Jersey
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In addition to all the accurate advice Ted sent to you, you may
need also to know that bare unpainted chromate conversion coatings
are limited to a surface temperature of 140 F, above which the
coatings disintegrate. Absolutely not suitable for a very hot sink.
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The coating of choice for heat sinks has been electroless nickel
forever. Corrosion resistant, conductive, both thermal and
electrical. Even looks good.
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Anodizing should be fine. Aluminum oxide is tough, proven, and is
thermally a good conductor due to lattice phonon effects.
Dale Woika
- Bellefonte, PA, USA
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Electroless nickel is the best coating if you want maximum heat
transfer. Anodize coatings are dielectric and have poor heat transfer
characteristics. They are very corrosion resistant as is electroless
nickel.
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